After the
events of September 11th, one thing everyone seems to agree about is that
life in the U.S.A. will never be the same. One of lifeís changes will surely involve
management of real-time spatial data, specifically for tracking moving objects -- people,
cars, trucks, trains, emergency vehicles, jets -- for security purposes as well as for
the nascent locationbased services (LBS) market. Bit by bit, real-time spatial data is
pervading our traditional static spatial applications. This column summarizes the
challenges of real-time data processing and surveys the key players offering solutions.

Ephemeral locations. Real-time spatial data are records of the locations of
ephemeral real-world events, such as the rapidly changing coordinates of a moving
vehicle. The steps in processing real-time spatial data are:

capturing information about an eventís coordinates and date- and
time-stamping those coordinates using such technology as GPS;

transmitting that data to a central machine;

storing the information in the organized structure of a database;

analyzing the data both as they arrive and statistically over time;

if the analyses dictate, sending messages to other systems to inform
them of the status of the object being monitored (see Figure 1).

Figure 1: Conceptual diagram of realtime information flow from the event source
(GPS device) to a storage point (database) to a userdecipherable message, such as a
map or e-mail.

In other words, peopleís mobile devices (cell phones, PDAs, in-vehicle systems, GPS
receivers) transmit their locations to a central database at regular intervals. The
database determines relationships among moving objects (mobile-to-mobile tracking) or
between moving and stationary objects (mobile-to-static tracking). If a relationship
has significance, the database sends a message to a decision-maker.